Please post your prints so I know if I am wasting my time :-)

Scaled for 3.75 inch action figures.

The Pauldron fits over any figures chest. It is attached to ARC backpack and ARC armor so it fits nice and snug.

The Kama's belt will fit on top of most figures. Integrates into the existing figures belt. It adds a few ARC style pouches to the figures own existing belt. There are cut outs in the back so the existing figure's thermal detonator fit nicely.

The helmet... well... find that on your own. There are so many diff sizes of head ball joints that making a helmet that fits all of them would be impossible.

Remixes below plus remix of https://www.thingiverse.com/thing:3113123 for the Rex I tried.